Revenue rose 40% to nearly $1.6 billion in the fourth quarter, above analyst estimates. That marked the first growth acceleration since Facebook started selling shares to the public in May.

Facebook said it earned $64 million, or 3 cents a share, compared with $302 million, or 14 cents a share, a year earlier.

"In 2012, we connected over a billion people and became a mobile company," Chief Executive Mark Zuckerberg said in a written statement that accompanied the fourth-quarter financial results. "We enter 2013 with good momentum and will continue to invest to achieve our mission and become a stronger, more valuable company."

Since Facebook's overhyped initial public offering landed on Wall Street with a big thud, the company has had a tough time winning friends there.

"I don't think any investors are going to unfriend Facebook for these numbers. I think the stock is trading down a bit because people were expecting a blowout quarter, and what they got was a good-but-not-great quarter," said Bill Burnham with hedge fund Inductive Capital.

Facebook shares fell 3% in after-hours trading after the fourth-quarter results were released.

Investors will be listening for clues this afternoon whether Facebook has made progress in reinventing itself as a mobile business. It's a challenge it must meet to retain users and regain its luster on Wall Street.

How successful the company has been in that quest became clearer in its fourth-quarter earnings report. Mobile advertising accounted for about 23% of ad revenue in the quarter, up from 14% in the third quarter, Facebook said. The figure was in the ballpark of what analysts had expected.

Mobile ads have become increasingly important for Facebook as more of its users check their News Feed on their smartphones and tablets rather than on personal computers.

Signs that mobile ads were starting to gain traction have pushed up Facebook shares, which reached rock bottom in early September.

Facebook has also rolled out new applications for the iPhone and mobile phones powered by Android software. But not everything has a mobile focus. There is no mobile version of Graph Search, which Facebook rolled out this month.